This invention relates to arrays of optical fibers, and, more particularly, to passive spatial scanners, optical memories, image converters and other optical apparatus utilizing same.
Optical memories proposed by many workers in the laser art typically include an optical scanner to perform the necessary read and write functions. Most commonly the scanner utilizes an active device, such as an electro-optic or acousto-optic modulator, to deflect a laser beam in raster fashion. In this type of active scanner, however, important parameters such as bandwidth, the number of resolvable spots, and drive power involve numerous trade-offs which, in conjunction with inherent materials restrictions, limit their usefulness in optical memories as well as in numerous other applications including real-time display devices, hard copy reproduction devices, carrier modulators and the like. Described hereinafter, however, is a passive scanner in accordance with my invention which reduces significantly many of the foregoing problems encountered with active scanners.
Similar trade-offs arise in the design of image converters, especially where the image to be detected is virtually instantaneous. An example of the latter is a picosecond light pulse. In recent years many techniques have been developed to display and measure such light pulses; e.g., two-photon fluorescence, picosecond streak cameras, light-in-flight photographic techniques and echelon techniques, all of which typically display the pulse on photographic film. Unfortunately, the nonlinearity and limited dynamic range of fast photographic film entail time-consuming photodensitometry and limit the practical usefulness of these methods. Although picosecond pulses can also be measured utilizing second harmonic generation, many laser shots are required so that it may take several hours to obtain one pulse display. The problem is further compounded by the irreproducibility of present high-power picosecond-pulse lasers. Described hereinafter, however, is an optical sampling oscilloscope in accordance with my invention which gives instantly a linear display of a single picosecond pulse on a nanosecond real-time oscilloscope.